EBBINGHAUS, H. (1913). Memory, a contribution to experimental psychology. Teachers College, Columbia...

7/25/2019 EBBINGHAUS, H. (1913). Memory, a contribution to experimental psychology. Teachers College, Columbia University. New York.pdf

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Columbia

teachers

College

Educational

IReprints

'

Wo.

3


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MEMORY

A

CONTRIBUTION

TO

EXPERIMENTAL

PSYCHOLOGY

BY

HERMANN

EBBINGHAUS

PRIVAT

DOCENT

IN

PHILOSOPHY

AT THE

UNIVERSITY

OF

BERLIN

(1885)

De

subjecto

vetustissimo

novissimam

promovemus

scienttam

TRANSLATED

BY

HENRY A.

RUGER,

Pn.D.

ASSISTANT

PROFESSOR

OF

EDUCATIONAL

PSYCHOLOGY,

TEACHERS

COLLEGE,

COLUMBIA

UNIVERSITY

AND

CLARA

E.

BUSSENIUS

PUBLISHED BY

flfolkgr,

Ctttmbte

Ihmir

rmti;

NEW

YORK CITY


8/142

Lb

i

06,3

602497


9/142

TRANSLATORS'

INTRODUCTION

The

publication

by

Ebbinghaus

of

the results

of

his

experi-

mental

investigation

of

memory (1885)

marks the

application

of

precise

scientific method to the

study

of the

higher

mental

pro-

cesses.

By

his

invention

of nonsense

syllables

as

the

material

to

be

thus

employed

Ebbinghaus

signalised

the

growing

independ-

ence

of

experimental

psychology

from

physics

and

physiology.

For

educational

psychology

his

work

is

of

especial importance

because the

field

in

which

he

worked

was

that

of the

ideational

processes

and because

the

problems

which

he

attacked

were

functional

and

dynamic.

The

problem

of

the

most

efficient

dis-

tribution of

repetitions

in

committing

material

to

memory

may

be

taken

to

illustrate

the

identity

in

the

nature

of

the questions

investigated

by

him and

those

of

especial

interest to

us

to-day.

Despite

the

fact

that his

experiments

were

performed

only

on

himself and

that the

numerical

results

obtained

are

consequently

limited

in

significance,

his

work

stands

as an

embodiment of

the

essentials

of scientific

method.

On account of

its historical

importance

and

also

because

of its

intrinsic

relation

to

present

day

problems

and

methods

Ebbinghaus's

investigation

should

be

known as

directly

as

possible

by

all

serious students

of

psy-

chology.

To

facilitate

this

acquaintance

is

the

purpose

of this

translation.

The

translators

wish

to

acknowledge

their

indebtedness to

Professors Edward

L.

Thorndike,

Robert S.

Woodworth,

and

E.

W.

Bagster-Collins

of Columbia

University,

to

Professor

Walter

Dill

Scott

of

Northwestern

University

and

to

Mrs. H.

A.

Ruger

for

assistance

in

revising manuscript

and

proof.


10/142


11/142

AUTHOR'S

PREFACE

In

the

realm of mental

phenomena,

experiment

and measure-

i

ment

have

hitherto been

chiefly

limited

in

application

to

sense

perception

and

to

the

time relations

of mental

processes.

By

means

of

the

following

investigations

we

have

tried to

go

a

step

farther

into

the

workings

of

the

mind

and

to

submit

to

an

experimental

and

quantitative

treatment

the

manifestations

of

memory.

The

term,

memory,

is

to

be

taken

here

in its

broadest

sense,

including Learning,

Retention,

Association

and

Repro-

duction.

The

principal objections

which,

as a

matter of

course,

rise

against

the

possibility

of

such

a

treatment are

discussed

in

detail in

the

text

and

in

part

have

been

made

objects

of

investi-

gation.

I

may

therefore ask those

who are

not

already

convinced

a

priori

of

the

impossibility

of

such an

attempt

to

postpone

their

decision about its

practicability.

The

author

will be

pardoned

the

publication

of

preliminary

results

in

view

of the

difficulty

of

the

subject

investigated

and

the

time-consuming

character of

the

tests.

Justice

demands

that the

many

defects

due

to

incompleteness

shall

not be

raised

as

objections

against

such

results. The

tests

were all made

upon

myself

and have

primarily

only

individual

significance.

Naturally

they

will not

reflect

exclusively

mere

idiosyncrasies

of

my

mental

organisation;

if the

absolute

values

found

are

throughout

only

individual,

yet

many

a

relation

of

general

validity

will

be

found

in

the

relation

of

these numbers

to

each

other

or

in

the

relations

of

the

relations.

But

where

this

is the case

and

where

it is

not,

I

can

hope

to

decide

only

after

finishing

the

further

and

comparative experiments

with

which

I

am

occupied.


12/142


13/142

TABLE

OF CONTENTS

Chapter

Page

Preface

.

.

.

v

I.

OUR

KNOWLEDGE

CONCERNING MEMORY

....

i

Section i.

Memory

in

its

Effects

i

2.

Memory

in

its

Dependence

....

3

3.

Deficiencies

in

our

Knowledge

concerning

Memory

.......

4

II.

THE

POSSIBILITY

OF ENLARGING OUR

KNOWLEDGE OF

MEMORY

7

Section

4.

The

Method

of Natural

Science

...

7

5.

The

Introduction

of

Numerical

Measurements

for

Memory

Contents

.....

8

6.

The

Possibility

of

Maintaining

the

Constancy

of Conditions

Requisite

for

Research

.

.

it

7.

Constant

Averages

.

.

. . .

12

8.

The

Law

of

Errors

15

9.

Resume

. .

. .

. .

.

.

19

10.

The

Probable Error

30

III.

THE

METHOD

OF

INVESTIGATION .

. . .

. .

22

Section n.

Series of

Nonsense

Syllables

23

12.

Advantages

of

the

Material

.

.

.

.

23

13.

Establishment

of

the

Most Constant

Experi-

mental

Conditions

Possible

.

.

. .

24

14.

Sources

of Error

26

15.

Measurement

of

Work

Required

...

30

16. Periods

of

the

Tests

33

IV. THE

UTILITY OF THE

AVERAGES

OBTAINED

. . .

.

34

Section

17.

Grouping

of the

Results

of the

Tests

. .

34

18.

Grouping

of

the

Results of

the

Separate

Series

41

V.

RAPIDITY

OF

LEARNING

SERIES

OF

SYLLABLES

AS

A

FUNCTION

\/

OF

THEIR

LENGTH

.......

46

Section

19.

Tests

Belonging

to

the Later

Period . .

46

20.

Tests

Belonging

to

the

Earlier

Period

.

.

49

21.

Increase

in

Rapidity

of

Learning

in

the

Case

of

Meaningful

Material

....

50

VI.

RETENTION

AS

A

FUNCTION OF

THE

NUMBER

OF

REPETITIONS

52

^

Section

22.

Statement

of

the

Problem

.

. . .

52

23.

The

Tests

and

their

Results ....

54

24.

The

Influence

of

Recollection

.

.

.

58


14/142

viii

Table

of

Contents

Chapter

Page

VII. RETENTION

AND

OBLIVISCENCE

AS

A

FUNCTION

OF

THE

TIME

62

Section

26.

Explanations

of

Retention and Obliviscence

.

62

27.

Methods

of

Investigation

of

Actual Conditions

65

28. Results

67

29.

Discussion

of

Results .....

76

30.

Control

Tests

79

VIII.

RETENTION

AS

A

FUNCTION OF

REPEATED

LEARNING .

.

81

Section

31.

Statement

of the

Problem and the

Investigation

81

32.

Influence of the

Length

of

the

Series

.

.

84

33.

Influence

of

Repeated

Learning

...

85

34.

Influence

of

the

Separate

Repetitions

. .

87

IRRETENTION

AS

A FUNCTION

OF

THE

ORDER

OF

SUCCESSION OF

THE

MEMBERS

OF THE

SERIES

.....

90

Section

35.

Association

according

to

Temporal

Sequence

and

its

Explanation

.....

90

36.

Methods

of

Investigation

of

Actual

Behavior

95

37.

Results.

Associations

of

Indirect

Sequence

.

99

38.

Experiments

with

Exclusion of

Knowledge

.

101

39.

Discussion

of

Results

.....

106

40.

Reverse

Associations

.

.

.

.

.no

41.

The

Dependence

of

Associations

of

Indirect

Sequence

upon

the

Number of

Repetitions

.

114

42.

Indirect

Strengthening

of

Associations

.

.

117


15/142

MEMORY

CHAPTER

I

Section

i.

Memory

in

its

Effects

The

language

of

life

as well

as of

science

in

attributing

a

memory

to

the

mind

attempts

to

point

out the facts

and their

interpretation

somewhat

as

follows:

Mental states of

every

kind,

sensations,

feelings,

.

ideas,

{

which

were

at one

time

present

Jn

consciousness

and

then

have

.

disappeared

from

it.

have

not with

their

disappearance

absolutely

ceased

to exist.

Although

the

inwardly-turned

look

may

no

longer

be

able to

find

them,

nevertheless

they

have not

been

utterly

destroyed

and

annulled,

but in a certain

manner

they,

continue to

exfet,

sjoreiTul^jro

to

speak,

.in.

the

memory.

We

cannot^of

course,

directly

observe_their

present

existence,

but

it

is

revealed

by

the effects

which

come

to

our

knowledge

with

a

certainty

like

that

with

which

we

infer

the existence

of

the

stars

below

the

horizon.

These

effects

are of different

kinds.

In

a

first

group

of

cases we can call

back

into

conscious-

ness

by

an

exertion of

the

will

directed to this

purpose

the

seemingly

lost

states

(or,

indeed,

in

case these

consisted

in

imme-

diate

sense-perceptions,

we

can

recall

their

true

memory

images)

:

that

is,

we can

reproduce

them

voluntarily. During

attempts

of

this

sort,

that

is,

attempts

to

recollect

all

sorts

of

images

toward

which

our

aim

was

not

directed,

accompany

the

desired

images

to

the

light

of

consciousness.

Often,

indeed,

the

latter

entirely

miss

the

goal,

but as

a

general thing

among

the

repre-

^

sentations is

found

the

one

which we

sought,

and

it

is imme-

\

diately

recognised

as

something

formerly

experienced.

It

would

be

absurd

to

suppose

that

our will has created

it

anew

and,

as


16/142

2

Memory

or

somewhere.

The

will,

so

to

speak,

has

only

discovered

it

and

brought

it to

us

again.

In

a

second

group

of

cases

this

survival

is

even

more

striking.

Often,

even

after

years,

mental

states

once

present

in

conscious-

ness

return

to

it

with

apparent

spontaneity

and

without

any

act

of

the

will;

that

is,

they

are

reproduced^

involuntarily.

Here,

also,

in the

majority

of

cases

we

at once

recognise

the

returned

mental

state

as

one

that

has

already

been

experienced;

that

is,

we

remember

it.

Under

certain

conditions,

however,

this

ac-

companying

consciousness

is

lacking,

and

we

know

only

indi-

rectly

that the

now

must

be identical

with

the

then

;

yet

we

receive

in

this

way

a

no

less

valid

proof

for

its existence

during

the

intervening

time.

As more

exact

observation

teaches

us,

the

occurrence

of

these

involuntary

reproductions

is

not

an

entirely

random

and

accidental

one.

On the

contrary

they

are

j^

brought

about

through

the

instrumentality

of

other,

immediately

present

mental

images.

Moreover

they

occur

in

certain

regular

ways

which

in

general

terrns

are

described

under

the

so-called

ffrAlaws

of

association^

Finally

there

is

a

third

and

large group

to

be

reckoned

with

here.

The vanished

mental

states

give

indubitable

proof

of

their

continuing

existence

.even

if

they

themselves

do

not

return to

V

consciousness

at

all,

or at least

not

exactly

at

the

given

time.

Employment

of a

certain

range

of

thought

facilitates

under

cer-,

tain

conditions the

employment

of

a

similar

range

of

thought,

even

if

the

former

does

not

come

before the mind

directly

either

in

its

methods

or in

its

results.

The

boundless

domain

of

the

\

effect

of

accumulated

experiences

belongs

here.

This

effect

results

from

the

frequent

conscious

occurrence

of

any

condi-

tion or

process,

and

consists in

facilitating

the

occurrence

and

progress

of

similar

processes.

This

effect

is

not

fettered

by

the

condition

that

the

factors

constituting

the

experience

shall

return

in

toto

to

consciousness.

This

may

incidentally

be the

case

with

a

part

of

them;

it

must

not

happen

to

a

too

great

extent

and

with

too

great

clearness,

otherwise

the

course of

the

present

process

will

immediately

be

disturbed.

Most of

these

experiences

remain

concealed

from

consciousness

and

yet pro-

duce an

effect

which

is

significant

and

which

authenticates

their


17/142

Our

Knowledge

Concerning

Memory

3

Section

2.

Memory

in

its

Dependence

Along'

with

this

bare

knowledge

of

the

existence

of

memory

and

its

effects,

there

is

abundant

knowledge

concerning

the

conditions

upon

which

depend

the

vitality

of

that

inner

survnljal'

as well as the

fidelity

and

promptness

of

the

reproduction.

\\

How

differently

do different

individuals

behave

in

this

respect

One

retains and

reproduces

well;

another,

poorly.

And

not

only

does

this

comparison

hold

good

when

different

individuals are

compared

with

each

other,

but

also when

different

phases of

the

existence

of

the

same

individual

are

compared:

morning

and

evening, youth

and

old

age,

find

him

different

in/

this

respect.

Differences

in

the content of the

thing

to be

reproduced

are

\

of

great

influence. Melodies

may

become

a

source

of

torment

_'_

by

the

undesired

persistency

of

their

return.

Forms

and

colors

are

not

so

importunate;

and

if

they

do

return,

it is

with

notice-

able

loss

of

clearness

and

certainty.

The

musician

writes for

the

orchestra what

his

inner

voice

sings

to

him;

the

painter

rarely

relies

without

disadvantage

solely

upon

the

images

which

his

inner

eye

presents

to

him;

nature

gives

him his

forms,

study

1

governs

his

combinations of

them. It

is with

something

of

a

struggle

that

past

states

of

feeling

are

realized;

when

realized,

and this

is

often

only through

the

instrumentality

of

the move-

ments which

accompanied

them,

they

are

but

pale

shadows

of

themselves.

Emotionally

true

singing

is rarer than

technically

correct

singing.

If

the

two

foregoing

points

of

view are taken

together

differences

in

individuals and

Differences

in

content

an

endless

number

of differences

come to

light.

One

individual overflows

with

poetical

reminiscences,

another

directs

symphonies

from

memory,

while numbers

and

formulae,

which

come

to

a third

without

effort,

slip

away

from the other two

as

from

a

polished

stone.

Veryjyreat

is

the^dependence

_

of

retention

and-jffimvlnciion

upon

the

inten^iyoijhe_attention

and

interest

which

were

attached

to

the

mental

states the first

time

they

were

present.

The

burnt

child shuns

the

fire,

and the

dog

which

has


18/142

4

Memory

and

yet

not

be

able

to

recall

the

color

of their

hair

or

of

their

eyes.

Under

ordinary

circumstances, indeed,

frequent

repetitions

are

indispensable

in

order

to

make

possible

the

reproduction

of a

given

content.

Vocabularies,

discourses,

and

poems

of

any

length

cannot

be

learned

by

a

single

repetition

even

with

the

greatest

concentration

of

attention

on

the

part

of

an

individual of

very

great

ability.

By

a sufficient

number of

repetitions

their

final

mastery

is

ensured,

and

by

additional

later

reproductions

gain

in

assurance

and

ease

is

secured.

)

/

Left

to

itself

every

mental

content

gradually

loses

its

capacity

/

for

being

revived,

or

at least

suffers^

loss_in

this

regard

under

\

the

influence

of

time.

Facts crammed

at

examination

time

soon

vanish,

if

they

were

not

sufficiently grounded

by

other

study

and later

subjected

to

a

sufficient review.

But

even

a

thing

so

early

and

deeply

founded

as

one's

mother

tongue

is

noticeably

impaired

if

not used for several

years.

Section

3.

Deficiencies

in

our

Knowledge

concerning

Memory

The

foregoing

sketch

of

our

knowledge

concerning

memory

makes

no claim

to

completeness.

To

it

might

be

added such

a

series

of

propositions

known

to

psychology

as the

following:

''

He

who

learns

quickly

also

forgets

quickly, Relatively

long

series

of ideas

are

retained

better

than

relatively

short

ones,

Old

people

forget

most

quickly

the

things they

learned

last,

and

the

like.

Psychology

is wont

to

make

the

pictu-re

rich

with

anecdote

and

illustration.

But

and this

is the

main

point

even

if

we

particularise

our

knowledge

by

a most

extended

use

(.of

illustrative

material,

everything

that

we can

say

retains

the

indefinite,

general,

and

comparative

character

of

the

propositions

quoted

above.

Our information

comes

almost

exclusively

from

the

observation

of

extreme

and

especially

striking

cases.

We

are

able

to describe

these

quite

correctly

in

a

general way

and

in

vague expressions

of

more

or

less.

We

suppose, again

quite

correctly,

that

the

same influences

exert

themselves,

although

in

a less

degree,

in

the

case

of

the

inconspicuous,

but a thousand-

fold

more

frequent,

daily

activities

of

memory.

But

if

our

i

.'

curiosjty__

carries

us

further

and we

crave

more

specific

and


19/142

Our

Knowledge

Concerning

Memory

5

dependencies,

both those

already

mentioned

and

others,

if we

put questions,

so to

speak,

concerning

their

inner structure our

answer

is

silence.

HQW

does

the

disappearance

of

the

ability

to

reproduce,

forgetfulness,

depend

upon

the

length

of

,

time

^during

which

^a_mp_ekiQps

have

taken

place?

What,

proportion

does

the

increase

in

the

certainty

of

reproduction

bear to the number

ojj^petitions

?

How

do

these

relations

vary

with

the

greater

or

less

intensity

of the interest

in

the

thing

to'

be

reproduced

?

These

and similar

questions

no

one

can

answer.

This

inability

does

not

arise

from

a

chance

neglect

of

investi-

gation

of

these

relations.

We

cannot

say

that

tomorrow,

or

whenever we wish

to

take

time,

we

can

investigate

these

prob-

lems.

On the

contrary

this

inability

is

inherent

in

the

nature

of the

questions

themselves.

Although

the

conceptions

in

ques-

tion

namely,

degrees

of

forgetfulness,

of

certainty

and interest

are

quite

correct,

we

have

no means

for

establishing

such

degrees

in

our

experience

except

at

the

extremes,

and even

then

we

cannot

accurately

limit those extremes.

We

feel

therefore

that we are

not at

all

in

a

condition

to

undertake

the

investiga-

tion.

We form

certain

conceptions

during

striking

experiences,

but

we cannot find

any

realisation of

them

in

the

similar but less

striking experiences

of

everyday

life. Vice

versa there are

prob-~

ably

many conceptions

which

we

have

not

as

yet

formed

which

would

be serviceable

and

indispensable

for

a

clear

understanding

of

the

facts,

and

their theoretical

mastery.

The

amount

of

detailed information

which

an

individual

has

at

his

command

and

his

theoretical

elaborations

of

the

same

are

rnutually_,dep_endent

;

they grow

in and

through

each

other.

It

is

because

of the

indefinite and little

specialised

character

of

our

knowledge

that

the

theories

concerning

the

processes

of

memory, reproduction,

and association

have

been

up

to the

present

time

of so

little

value

for

a

proper

comprehension

of

those

processes.

For

example,

to

express

our

ideas

concerning

their

physical

basis

we use

different

metaphors

stored

up

ideas,

engraved

images,

well-beaten

paths.

There

is

only

one

thing

certain about

these

figures

of

speech

and that

is

that

they

are

not

suitable.

Of

course the existence

all

these

deficiencies has its


20/142

6

Memory

of

the

clearest

insight

into

the

inadequacy

of

our

knowledge,

we

shall

ever

make

any

actual

progress.

Perhaps

we

shall

always

have

to

be

resigned

to

this.

But

a

somewhat

greater

accessibility

than

has so

far

been realised

in

this

field cannot be

denied

to

it,

as

I

hope

to

prove presently.

If

by

any

chance

a

way

to

a

deeper

penetration

into

this matter

should

present

itself,

surely,

considering

the

significance

of

memory

for

all

mental

phenomena,

it

should

be

our

wish

to

enter

that

path

at once.

For

at the

very

worst

we should

prefer

to

see

resignation

arise

from

the failure

of

earnest

investigations

rather

than

from

persistent,

helpless

astonishment

in

the

face

of

their

difficulties.


21/142

CHAPTER

II

THE

POSSIBILITY OF

ENLARGING

OUR

KNOWL-

EDGE OF

MEMORY

Section

4.

The

Method

of

Natural

Science

ywA^ftC*

****

The

^method

of

obtaining

exact

measurements

i.e.,

numer-

ically

exact

ones

of the

inner structure of causal

relations

-is,

by

virtue

of

its

nature,

of

general

validity. This^Rthod,(

indeed)

has

been

so

exclusively

used and

so

fully

worked

out

by

the natural

sciences

that,

as

a

rule,

it is

defined

as

something

peculiar

to

them,

as

the

method of

natural

science.

To

repeat,

however,

its

logical

nature

makes

it

generally applicable

to

all

spheres

of existence

and

phenomena.

Moreover,

the

possibility

of

defining accurately

and

exactly

the actual behavior

of

any

process whatever,

and

thereby

of

giving

a

reliable

basis

for

the

direct

comprehension

of

its

connections

depends

above

all

upon

the

possibility

of

applying

this method.

We

all

know of

what this

method consists: an

attempt

is

f\

6/*\ 'I

J

/

.

of

these

conditions~IT

Isolated

from

the

rest and

jrarted:

in a

CJ

T*~

way

that can be

numerically

described;

then

the

accompanying

change

on the side

of the effect

is

ascertained

by

measurement

or

computation.

Two

fundamental

and insurmountable

difficulties,

seem,

how-

ever, to

oppose

a

transfer

of

this

method

to

the

investigation

of

the causal

relations

of

mental events in

general

and

of those of

memory

in

particular.

In

the

first

place,

how are

we to

keep

even

approximately

constant the

bewildering

mass

of

causal

conditions

which,

in

so

far as

they

are

of

mental

nature,

almost

completely

elude

our

control,

and

which,

moreover,

are

subject

to

endless and

incessant

change?

In

the

second

place,

by

what

'I

J

/


22/142


23/142

Possibility

of

Enlarging

Our

Knowledge

of Memory

9

poem.

After

a

shorter

time

we

should

expect

to

find

the

dif-

ference

greater;

after

a

longer

time

we

should

expect

to

find

it

less.

If

'the first

committing

to

memory

is

a

very

careful

and

long

continued

one,

the

difference

will

be

greater

than

if

it

is

desultory

and soon

abandoned.

In

short,

we have

without

doubt

in

these

differences

numerical

expressions

for

the

difference between

these

subliminally

per-

sistent

series

of

ideas,

differences which

otherwise

we

would

have to

take

for

granted

and

would

not

be

able

to

demonstrate

by

direct

observation. Therewith

we

have

gained

possession

of

something

that

is at

least

like

that

which

we

are

seeking

in

our

attempt

to

get

a

foothold

for the

application

of

the

method of the natural

sciences :

namely, phenomena

on

the

side

of the

effects which

are

clearly

ascertainable,

which

vary

in

accordance

with

the

variation

of

conditions,

and which

are

capable

of numerical

determination.

Whether we

possess

in

them

correct

measures

for

these

inner

differences,

and

whether

/

we

can

achieve

through

them

correct

conceptions

as

to

the causal

relations

into which this

hidden

mental

life

enters

these

ques-'

tions

cannot

be

answered

a

priori. Chemistry

is

just

as

little

able to determine

a

priori

whether

it is

the

electrical

phenomena,

or

the

thermal,

or some

other

accompaniment

of

the

process

of

chemical

union,

which

gives

it its

correct

measure

of

the effective

forces of

chemical

affinity.

There

is

only

one

way

to do

this,

and

that is to

see whether

it is

possible

to

obtain,

on

the

pre-

supposition

of

the

correctness

of

such

an

hypothesis^

well

classi-

fied,

uncontradictory

results,

and correct

anticipations

of

the

future.

Instead

of

the

simple phenomenon

occurrence

or

non-occur-

rence

of a

reproduction

which admits

of

no

numerical

distinc-}

tion,

I

intend

therefore to consider

from

the

experimental

standpoint

a

more

complicated,

process

as

the

effect,

and I

shall

observe

and

measure

its

changes

as

the

conditions

are

variedU

By

this

I

mean

the artificial

bringing

about

by

an

appropriate

number

of

repetitions

of

a

reproduction

which

would

not occur

of

its

own

accord.

But in

order to

realise

this

experimentally,

two

conditions

at

least

must

be

fulfilled.


24/142

r Memory

process

of

learning

by

heart

is

completed.

For

if

the

process

of

learning by

heart

is sometimes

carried

past

that moment

and

sometimes

broken off

before

it,

then

part

of

the differences

found

under

the

varying

circumstances

would

be due

to

this

in-

equality,

and

it

would

be incorrect

to

attribute

it

solely

to

inner

differences

in

the

series

of

ideas.

Consequently

among

the

different

reproductions

of,

say,

a

poem, occurring

during

the

process

of

its

memorisation,

the

experimenter

must

single

out

one' asi

especially

characteristic,

and be able to

find

it

again

with

practical

accuracy.

__In

the

second

place

the

presupposition

must

be allowed

that

the

number

of

repetitions

by

means

of

which,

the other

condi-

tions

being unchanged,

this

characteristic

reproduction

is

brought

about

would

be

every

time

the

same.

For

if

this

number,

under conditions otherwise

equivalent,

is

now

this

and

now

that,

the differences

arising

from

varied

conditions

lose,

of

course,

all

significance

for the

critical evaluation

of

those

varying

conditions.

Now,

as

far

as the

first

condition

is

concerned,

it

is

easily

fulfilled

wherever

you

have

what

may

properly

be called

learn-

ing by

heart,

as

in

the case

of

poems,

series

of

words,

tone-

sequences,

and

the

like.

Here,

in

general,

as

the

number

of

repetitions increases, reproduction

is

at

first

fragmentary

and

halting;

then it

gains

in

certainty;

and

finally

takes

place

smoothly

and

without error. The

first

reproduction

in which

this last result

appears

can

not

only

be

singled

out

as

especially

characteristic,

but

can

also be

practically

recognised.

For

con-

venience

I

will

designate

this

briefly

as

the

first

possible

repro-

duction.

The

question

now is:

Does

this fulfill

the

second

condition

mentioned

above?

Is

the

number

of

repetitions

necessary

to

bring

about

this

reproduction

always

the

same,

the other con-

ditions

being

equivalent?

However,

in

this

form,

the

question

will

be

justly

rejected

because it

forces

upon

us,

as if it

were

an

evident

supposition,

the

real

point

in

question,

the

very

heart

of

the

matter,

and

admits

of none but

a

misleading

answer.

Anyone

will

be

ready

to

admit

without

hesitation

that this relation of

dependence

will

be the

same

if

perfect

equality

of

experimental

conditions


25/142

Possibility

of

Enlarging

Our

Knowledge

of

Memory

1 1

has

hardly

ever been

misunderstood

by

anybody

so

far

as

to

come in here. But this

theoretical

constancy

is of

little value:

How

shall I

find it

when

the

circumstances

under

which

I

am

actually

forced

to

make

my

observations

are

never

the same?

So

I

must rather ask:

Can

I

bring

under

my

control

the

in-

evitably

and

ever

fluctuating

circumstances

and

equalise

them

to such

an

extent

that

the

constancy

presumably

existent

in

the

causal

relations

in

question

becomes

visible

and

palpable

to

me?

Thus

the

discussion

of

the

one

difficulty

which

opposes

an

exact

examination

of the

causal

relations

in

the mental

sphere

has

led

us

of

itself

to

the

other

(4).

A

numerical

determinsT )

tion

of

the

interdependent

changes

of cause

and

effect

appears

indeed

possibl/

if)only

we can

realise

the

necessary

uniformity

of

the

significant

conditions

in

the

repetition

of

our

experiments.

Section 6.

The

Possibility

of

Maintaining

the

Constancy

of

Conditions

Requisite

for

Research

He

who

considers the

complicated

processes

of

the

higher

mental life

or

who

is

occupied

with

the

still

more

complicated

phenomena

of

the

state and of

society

will

in

general

be

inclined

to

deny

the

possibility

of

keeping

constant the conditions

for

psychological

experimentation.

Nothing

is

more

familiar

to

us

than

the

capriciousness

of

mental

life

which

brings

to

nought

all

foresight

and calculation. Factors

which

are to the

highest

degree

determinative

and

to the

same

extent

changeable,

such

as

mental

vigor,

interest

in

the

subject,

concentration

of

atten- p>

tion,

changes

in

the course of

thought

which have

been

brought

about

by

sudden fancies

and

resolves

all

these

are either not at

all

under

our

control

or

are

so

only

to

an

unsatisfactory

extent.

V

However,

care must

be

taken

not to

ascribe

too

much,

weight

to

these

views,

correct

in

themselves,

when

dealing

with

fields

other

than

those

of

the

processes

by

the

observation

of

which

these

views

were

obtained.

All

such

unruly

factors

are

of

the

greatest importance

for

higher

mental

processes

which occur

only

by

an

especially

favorable

concurrence

of

circumstances.

The more

lowly,

commonplace,

and

constantly

occurring pro-

cesses are not

in

the least

withdrawn

from

their

influence,

but

we

have

it

for

the most

part

in

our

power,

when

it

is a

matter


26/142

Memory

or

less

accuracy

according

to

the

degree

of

interest;

it

is

con-

stantly

given

other

directions

by

the

change

of

external

stimuli

and

by

ideas.

But,

in

spite

of

that,

we

are

on

the whole

sufficiently

able

to

see

a house

just

when

we

want

to see

it

and

to receive

practically

the

same

picture

of

it ten

times

in suc-

cession

in

case

no

objective

change

has occurred.

There

is

nothing

a

priori

absurd

in

the

assumption

that

ordin-

l

ary

retention

and

reproduction,

which,

according

to

general

agreement,

is

ranked

next

to

sensorial

perception,

should

also

behave

like

it

in

this

respect.

Whether

this

is

actually

the

case or

not,

however,

I

say

now

as

I said

before,

cannot be

decided

in

advance.

Our

present

knowledge

is much

too

frag-

mentary,

too

general,

too

largely

obtained

from

the extraordin-

ary

to

enable

us

to

reach

a decision

on

this

point by

its

aid

;

at

must

be

reserved for

experiments

especially

adapted

to

that

urpose.

We must

try

in

experimental

fashion

to

keep

as

constant

as

possible

those

circumstances

whose influence

on

retention

and

reproduction

is

known

or

suspected,

and

then

ascertain

whether

that

is sufficient. The material

must be

so

hosen that

decided

differences

of interest

are,

at least

to

all

ppearances,

excluded;

equality

of attention

may

be

promoted

iy

preventing

external

disturbances;

sudden

fancies are not

Subject

to

control,

but,

on the

whole,

their

disturbing

effect is

limited

to

the

moment,

and will be of

comparatively

little account

[f

the

time

of

the

experiment

is

extended,

etc.

When,

however,

we

have

actually

obtained in

such

manner

/

the

greatest

possible

constancy

of

conditions

attainable

by

us,

(^

jfnow

are

we

to

know

whether this

is

sufficient for our

purpose

?

When

are

the

circumstances,

which

will

certainly

offer differ-

ences

enough

to keen

observation,

sufficiently

constant?

The

answer

may

be

made :

When

upon repetition

of

the

experiment

the results

remain

constant.

The

latter

statement

seems

simple

enough

to

be

self-evident,

but

on

closer

approach

to

the

matter

still

another

difficulty

is

encountered.

Section

7.

Constant

Averages

When

shall

the results

obtained

from

repeated experiments

under

circumstances

as

much

alike

as

possible

pass

for

constant


27/142

Possibility

of

Enlarging

Our

Knowledge

of Memory

1

3

value

as

the

other

or

at

Isast

deviates

so little'

from it

that

the

difference

in

proportion

to

its

own

quantity

and for

our

pur-

poses

is

of no

account

?

Evidently

not. That

would be

asking

too

much,

and is

not

necessarily

obtained

even

by

the natural

sciences.

Then,

perhaps

it is when

the

avejrages

from

larger

groups

of

experiments

exhibit the

characteristics

mentioned

above?

Again

evidently

not.

That

would

be

asking

too

little.

For,

if

observation

of

processes

that

resemble each

other

from

any

point

of view are

thrown

together

in

sufficiently

large

numbers,

1

fairly

constant

mean

values are

almost

everywhere

obtained

which,

nevertheless,

possess

little

or

no

importance

for the

pur-

poses

which

we

have

here.

The

exact

distance

of

two

signal

poles,

the

position

of a star

at

a

certain

hour,

the

expansion

of a

metal

for

a certain

increase

of

temperature,

all

the

numer-

ous coefficients

and

other constants

of

physics

and

chemistry

are

given

us as

average

values

which

only

approximate

to

a

high

degree

of

constancy.

On

the

other

hand

the

number

of

suicides

in

a

certain

month,

the

average

length

of

life in

a

given place,

the number

of

teams

and

pedestrians per

day

at

a certain

street

corner,

and

the

like,

are

also

noticeably

constant,

each

being

an

average

from

large groups

of observations. But both

kinds of

numbers,

which

I

shall

temporarily

denote

as

constants

of

natural

science

and statistical

constants, are,

as

everybody

knows,

con-

stant from

different

causes

and

with

entirely

different

significance

for

the

knowledge

of

causal

relations.

These

differences

can be

formulated

as

follows:

In

the

case

of

the constants

of

the natural

sciences each

indi-^>

vidual effect is

produced

by

a combination

of causes

exactly

x

>

~afike.j

The individual

values come

out

somewhat

differently

because

a

certain

number

or those

causes do

not

always join

the

combination

with

exactly

the same

values

(e.

g.,

there

are

little errors

in

the

adjustment

and

reading

of

the

instruments,

irregularities

in

the

texture or

composition

of

the

material

ex-

amined or

employed,

etc.).

However,

experience

teaches

us

that

this

fluctuation

of

separate

causes

does

not

occur

absolutely

irregularly

but

that

as a rule

it

runs

through

or,

rather,

tries

out

limited

and

comparatively

small

circles

of

values

symmet-


28/142

1

4

Memory

and

more

compensate

each

other and

thereby

be

swallowed

up

in

the

central

value

around

which

they

occur.

And

the final

result

of

combining

the

values will

be

approximately

the

same

as

if the

actually changeable

causes had

remained

the

same

not

only conceptually

but

also

numerically.

Thus,

the

average

value

is

in

these

cases the

adequate

numerical

representative

of

a

conceptually

definite

and

well limited

system

of

causal con-

nections;

if

one

part

of

the

system

is

varied,

the

accompanying

changes

of the

average

value

again give

the correct

measure

for

the

effect of those

deviations

on

the

total

complex.

On

the

other

hand,

no

matter

from

what

point

of

view

sta-

tistical

constants

may

be considered

it

cannot

be

said

of

them

that

each

separate

value

has resulted from

the combination

of

causes

which

by

themselves

had

fluctuated

within

tolerably

narrow limits and

in

symmetrical

fashion. The

separate

effects

arise,

rather,

from

an oftimes inextricable

multiplicity

of

causal

combinations

of

very

different

sorts, which,

to

be

sure,

may

share

numerous

factors

with each

other,

but

which,

taken

ag

a

whole,

have

no conceivable

community

and

actually

correspond

only

in

some

one

characteristic

of the effects. That

the

value

of the

separate

factors

must

be

very

different

is,

so

to

say,

self

evident.

That,

nevertheless,

approximately

constant values

ap-

pear

even

here

by

the

combining

of

large

groups

this fact

we

may

make

intelligible

by saying

that

in

equal

and

tolerably

large

intervals

of

time

or

extents of

space

the

separate

causal com-

binations

will be realised with

approximately

equal

frequency;

we

do

this

without

doing

more

than

to

acknowledge

as

extant a

peculiar

and

marvellous

arrangement

of

nature.

Accordingly

these

constant mean values

represent

no definite and

separate

causal

systems

but

combinations

of

such

which

are

by

no

means

of

themselves

transparent.

Therefore

their

changes

upon

varia-

tion

of

conditions

afford

no

genuine

measure of

the

effects

of

these

variations

but

only

indications

of

them.

They

are

of

no

direct

value

for the

setting

up

of

numerically

exact

relations

of

dependence

but

they

are

preparatory

to

this.

Let

us

now turn

back

to the

question

raised

at

the

beginning

of this

section.

When

may

we

consider

that

this

equality

of

conditions

which

we

have striven

to

realise

experimentally

has

been

attained

?

The

answer

runs as follows

:

When the


29/142

Possibility

of Enlarging

Our

Knowledge

of

Memory

1

5

when at

the

same

time

we

may

assume

that

the

separate

cases

V

belong

to

the same causal

system,

whose

elements,

however,

are

not

limited

to

exclusively

constant

values,

but

may

run

through

small

circles

of

numerical

values

symmetrical

around

a

middle

\

value.

Section

8.

The Law

of

Errors

Our

question,

however,

is

not

answered

conclusively by

the

statement

just

made.

Suppose

we

had

in

some

way

found

satis-

factorily

constant mean

values

for

some

psychical process,

how

would

we

go

about

it

to

learn

whether

we

might

or

might

not

assume

a

homogeneous

causal

condition,

necessary

for

their

further utilisation ?

4

The

physical

scientist

generally

knows

beforehand that he

will

have to

deal

with

a

single

causal

com-

bination,

the statistician knows that he has

to

deal with a mask

of

them,

ever inextricable

despite

all

analysis.

Both know

this

from the

elementary

knowledge

they

already possess

of the

.

nature

of the

processes

before

they

proceed

with

the

more

\

detailed

investigations. Just

as,

a

moment

ago,

the

present

knowledge

of

psychology

appeared

to

us too

vague

and unreli-

I

able to be

depended

upon

for

decision

about

the

possibility

of

constant

experimental

conditions

;

so

now

it

may

prove

insufficient

to

determine

satisfactorily

whether in

a

given

case we

have

to

>

deal

with

a

homogeneous

causal

combination

or

a

manifold

of

them

which chance

to

operate together.

The

question

is,

there-

fore,

whether

we

may

throw

light

on

the

nature

of

the

causation

of the

results

we

obtain

under

conditions

as

uniform

as

possible

by

the

help

of some other criterion.

The

answer

must

be:

This

cannot

be

done

with

absolute cer-

tainty,

but

can, nevertheless,

be

done

with

great probability.

Thus,

a

start

has

been

made

from

presuppositions

as

similar

as

possible

to

those

by

which

physical

constants

have

been obtained

and

the

consequences

which

flow

from

them

have

been

investi-

gated.

This

has

been

done for

the

distribution of

the

single

values

about

the

resulting

central

value and

quite

independently

of

the

actual

concrete characteristics of

the

causes.

Repeated

comparisons

of these calculated values

with

actual observations

have

shown

that

the

similarity

of

the

suppositions

is

indeed

great


30/142

1

6

Memory

in

this,

that

the

grouping

of

a

large

number

of

separate

values

that

have

arisen

from

causes

of

the

same

kind

and

with

the

modifications

repeatedly

mentioned,

may

be

correctly

represented

by

a

mathematical

formula,

the

so-called

Law

of

Errors.

This

is

especially

characterised

by

the fact

that

it

contains

but

one

unknown

quantity.

This

unknown

quantity

measures

the

relative

compactness

of

the

distribution of

the

separate

values

around

their

central

tendency.

It therefore

changes

according

to

the

kind of observation

and

is determined

by

calculation

from

the

separate

values.

NOTE. For

further information

concerning

this

formula,

which

is

not

here our

concern,

I must refer to

the

text-books

on

the

calculation

of

probabilities

and on

the

theory

of

errors. For

readers

unfamiliar

with

the

latter a

graphic

explanation

will

be

more

comprehensible

than a

statement and

discussion of

the

formula.

Imagine

a

certain observation

to

be

repeated

1,000

times. Each observation

as such

is

represented

by

a

space

of

one

square

millimeter,

and

its numerical

value,

or rather its

deviation

from

the

central

value of

the

whole

1,000 observations,

by

its

position

on

the

horizontal

line

p

q

of

the

adjoining

Figure

I.

For

every

observation

which

exactly

corresponds

with

the

central

value

one

square

millimeter is

laid

off on

the

vertical

line m n.

For

each

observed

value

which

deviates

by

one

unit

from the central value

upward

one

square

millimeter

is

laid

off

on

a

vertical

line

to

right

of

m

n

and distant one

millimeter

from

it,

etc. For

every

observed

value

which devi-

ates

by

x

units

above

(or

below)

the

central

value,

one

sq.

mm.

is

placed

on

a

vertical

line

distant

from

m

n

by

x

mms.,

to the

right

(or

left,

for

values

below

the central

value).

When

all

the observations

are

arranged

in

this

way

the

outer

contour

of

the

figure

may

be

so

compacted

that

the

projecting

corners

of

the

separate

squares

are

transformed into a

sym-

metrical

curve. If

now

the

separate

measures

are of

such a

sort

that their

central

value

may

be

considered

as

a

constant

as

conceived

by physical science,

the

form of the

resulting

curve

is

of

the

kind

marked

a

and

b

in

Fig.

I.

If the middle

value is a

statistical

constant,

the

curve

may

have

any

sort

of

a

form.

(The

curves a and

b with

the

lines

p q

in-

clude in

each

case

an

area

of

1,000

sq.

mms. This

is

strictly

the

case

only

with

indefinite

prolongation

of the curves and

the

lines

P

q,

but

these lines

and

curves

finally

approach

each other

so

closely

that

where

the

drawing

breaks

off

only

two

or

three

sq.


31/142

Possibility of

Enlarging

Our

Knowledge of

Memory

1

7

more

steep

or more flat

form

depends

on the

nature of

those

observations.

The more

exact

they

are,

the

more

will

they pile

up

around

the

central

value;

and

the

more

infrequent

the

large

deviations,

the

steeper

will

the

curve

be

and

vice versa.

For

the

rest the law of formation

of

the

curve

is

always

the

same.

Therefore,

if

a

person,

in

the case

of

any

specific

combination

of

observations,

obtains

any

measure of

the

compactness

of

distribution

of

the

observations,

he

can

survey

the

grouping

of

the

whole

mass. He

could

state,

for

instance,

how

often

a

deviation of a

certain value

occurs

and

how

many

deviations

fall

between certain

limits.

Or

as

I shall

show

in

what

follows

he

may

state

what amount

of

variation

includes between

itself-

and

the

central

value

a certain

per

cent of

all

the observed

values.

The

lines

-f-

w and w of

our

figure,

for

instance,

cut

out

exactly

the central

half

of

the

total

space representing

the obser-

vations.

But

in

the

case of

the

more

exact observations

of

I b

they

are

only

one

half

as

far from m

n

as

in

i a. So

the

state-


32/142

1 8

Memory

Therefore,

it

may

be said:

wherever

a

group

of

effects

may

be

considered

as

having

originated

each

time

from

the

same_

causal

combination,

which

was

subject

each time

only

to

so-

called

accidental

disturbances,

then

these

values

arrange

them-

selves

in

accordance

with

the

law of

errors.

However,

the

reverse of

this

proposition

is

not

necessarily

true,

namely,

that

wherever

a distribution of

values

occurs

according

to

the law of

errors

the

inference

may

be

drawn

that

this

kind

of

causation

has been at

work.

Why

should

nature not

occasionally

be

able

to

produce

an

analogous

group-

ing

in a more

complicated

way?

In

reality

this

seems

only

an

extremely

rare occurrence.

For

among

all the

groups

of

num-

bers

which

in

statistics

are

usually

condensed into

mean

values

not one

has

as

yet

been

found

which

originated

without

question

\

from

a number of

causal

systems

and

also

exhibited

the

arrange-

\

ment

summarised

by

the

law

of

errors.

1

Accordingly,

this law

may

be used as a

criterion,

not

an

abso-

lutely

safe

one

to

be

sure,

but

still

a

highly probable

one,

by

means of which

to

judge

whether

the

approximately

constant

mean values

that

may

be

obtained

by

any

proceeding may

be

employed experimentally

as

genuine

constants

of

science.

The

Law of

Errors does not

furnish

sufficient

conditions

for

such

a

use but it

does furnish

one of

the

necessary

ones.

The

final

explanation

must

depend upon

the

outcome

of

investigations

to

the

very

foundations

of

which

it

furnishes a

certain

security.

That is

why

I

applied

the

measure offered

by

it to answer our

still

unanswered

question:

If

the conditions

are

kept

as

much

alike

as is

possible,

is

the

average

number

of

repetitions,

which

is

necessary

for

learning

similar

series

to the

point

of

first

possible

reproduction,

a

constant

mean

value

in

the

natural

science

sense?

And

I

may

anticipate

by

saying

that

in

the

case

investigated

the

answer

has

come

out

in

the

affirmative.

x

The

numbers

representing

the

births

of

boys

and

girls

respectively,

as

derived

from

the total

number

of

births,

are

said

to

group

themselves

in

very

close

correspondence

with the

law

of

errors.

But in

this

case it

is

for

this

very

reason

probable

that

they

arise

from

a

homogeneous

combi-

nation

of

physiological

causes

aiming

so to

speak

at

the creation

of

a

well

determined

relation.

(See

Lexis,

Zur

Theorie

der

Massenerscheinungen

in

der

menschlichen

Gesellschaft,

p.

64

and

elsewhere

)


33/142

Possibility

of

Enlarging

Our

Knowledge

of

Memory

19

Section

p.

Resume

Two fundamental

difficulties arise in

the

way

of the

applica-

tion

of

the

so-called

Natural

Science

Method

to

the

examination

of

psychical processes:

(1)

The

constant flux

and

caprice

of

mental

events

do

not

admit of the

establishment

of

stable

experimental

conditions.

(2) Psychical processes

offer

no means

for

measurement

or

i

enumeration.

In

the

case

of the

special

field of

memory

(learning,

retention,

f

reproduction)

the

second

difficulty

may

be

overcome

to

a

certain

extent.

Among

the

external

conditions

of

these

processes

some

7

are

directly

accessible

to measurement

(the

time,

the

number

of

repetitions). They

may

be

employed

in

getting

numerical

values

indirectlywhere

that

would not

have

been

possible

directly.

We must

not

wait until

the

series

of ideas

committed

to

memory

,

return

to

consciousness

of

themselves,

but

we must

meet

them

halfway

and

renew them

to

such an

extent

that

they

may.jus^

\

be

reproduced

without

error. The

work

requisite

for

this

uncTer

certain

conditions

I

take

experimentally

as

a

measure

of the/

influence of

these

conditions

;

the

differences

in

the

work

which

appear

with a

change

of

conditions

I

interpret

as

a

measure

of

the

influence of

that

change.

Whether the

first

difficulty,

the

establishment of

stable

experi-

mental

conditions,

may

also

be

overcome

satisfactorily

cannot

be decided a

priori.

Experiments

must

be

made under conditions

as far as

possible

the

same,

to

see whether the

results,

which

will

probably

deviate from

one

another

when

taken

separately,

will furnish

constant

mean

values when

collected to

form

larger

groups.

However,

taken

by

itself,

this is

not sufficient to enable

us

to

utilise

such numerical

results for

the

establishment

of

numerical

relations

of

dependence

in

the

natural science sense.

Statistics

is

concerned with

a

great

mass

of

constant

mean

values that do

not

at all

arise

from

the

frequent

repetition

of

an

ideally

frequent

occurrence and

therefore

cannot

favor

further

insight

into it.

Such

is

the

great complexity

of

our

mental

life

that

it is

not

possible

to

deny

that constant

mean

values,

when

obtained,

are

of

the

nature of

such

statistical

con-


34/142

2O

.

Memory

to

the distribution

found

everywhere

in natural

science,

where

repeated

observation

of

the

-same

occurrence

furnishes different

separate

values,

I

suppose

tentatively

again

that

the

repeatedly

examined

psychical

process

in

question

occurred

each

time

under

conditions

sufficiently

similar for

our

purposes.

This

supposi-

tion

is

not

compulsory,

but is

very

probable.

If

it

is

wrong,

*

the continuation

of

experimentation

will

presumably

teach

this

by

itself: the

questions

put

from

different

points

of

v

view

will

lead

to

contradictory

results.

Section

10.

The

Probable Error

The

quantity

which

measures the

compactness

of the observed

values obtained

in

any

given

case and

which

makes

the

formula

which

represents

their distribution

a

definite one

may,

as

has

already

been

stated,

be

chosen

differently.

I

use

the

so-called

probable

error

(P.E.) i.e.,

that deviation

above

and

below

the mean value

which

is

just

as

often

exceeded

by-

the

separate

values

as

not

reached

by

them,

and

which,

therefore,

between

its

positive

and

negative

limits,

includes

just

half

of

all

the

observational

results

symmetrically arranged

around the

mean

value. As is

evident

from the

EBBINGHAUS, H. (1913). Memory, a contribution to experimental psychology. Teachers College, Columbia...

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Transcript of EBBINGHAUS, H. (1913). Memory, a contribution to experimental psychology. Teachers College, Columbia...